Mythbusters No. 6 - Stick's Doubling Rule for 3 away - 7 away or Greater

by Stick
27 August 2014


There was once a wise beyond his years backgammon player who went by the nick *Stick*. He prophesied that your future backgammon play at a certain set of particular scores would be greatly assisted by following this one simple rule.

Today we set out to see if the rule holds up to testing or if we'll have a busted myth.

Stick's Rule for 3a 7a or greater:

At 3 away 7 away or greater (3a 8a, 3a 9a, etc...) you should not double as the leader when there are significant gammon chances for either player.

Let's briefly stroll through a couple of details about the score and why this may be true before looking at the problems.

  • Your opponent's live cube take point is roughly around 18% or less depending on the exact score.

  • Your take point of a recube as the 3 away player is very high, at least 30%. This means that if your opponent takes your centered cube double his recube vig will be huge.

  • If you double you're changing the gammon values from a normal score value of .500 (rounded, will vary slightly AtS) to ~.350 or less for you and .550 or more for your opponent. You lower your gammon value and increase your opponent's.

  • Building on that is the obvious, when your opponent recubes, which he will be quick to do due to your already mentioned increased take point and the fact that it will be a dead cube, he will nullify your gammon value completely.

Keeping all of that in mind, see what you make of these problems all pulled from actual live over the board match play of Open level players. The analysis immediately follows the problem so scroll slowly. I will not discuss the problems individually as I normally due but after the problems will address the big question again.

Number 1

is Player 1

score: 4
pip: 166
11 point match
pip: 139
score: 8

is Player 2
on roll, cube action?

Analyzed in Rollout No double Double/Take
  Player Winning Chances: 74.40% (G:32.87% B:6.84%) 74.02% (G:33.27% B:11.12%)
  Opponent Winning Chances: 25.60% (G:4.21% B:0.31%) 25.98% (G:4.22% B:0.41%)
  Cubeless Equities +0.867 +1.324
Cubeful Equities
No double:+0.835±0.018 (+0.817..+0.853)
Double/Take:+0.769 (-0.065)±0.026 (+0.743..+0.795)
Double/Pass:+1.000 (+0.165)
Best Cube action: No double / Take
Percentage of wrong pass needed to make the double decision right: 22.1%
Rollout details
1296 Games rolled with Variance Reduction.
Dice Seed: 67903694
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 53 minutes 10 seconds

eXtreme Gammon Version: 2.19.206.pre-release, MET: Kazaross XG2

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